Function start_cooldown_in_slot 

pub(crate) fn start_cooldown_in_slot(
    state: &mut CombatState,
    buf: &mut DenseBuffer,
    recovery_local: LocalSpellIdx,
    slot_local: LocalSpellIdx,
    now: SimTime,
) -> u32

Start slot_local’s cooldown timers using recovery_local’s own recovery data.

An aura-332 action replacement shares the base action’s slot but keeps its own recovery time. SimC hands it the base’s shared cooldown_t (sc_demon_hunter.cpp:6927). It then writes the executing spell’s own duration in on every cast (:7002).